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Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:

  • Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into static friction ("stiction") between non-moving surfaces, and kinetic friction between moving surfaces. With the exception of atomic or molecular friction, dry friction generally arises from the interaction of surface features, known as asperities
  • Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other.
  • Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces.
  • Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body.
  • Internal friction is the force resisting motion between the elements making up a solid material while it undergoes deformation.


  • Friction
  • Thermodynamics
  • Heat


Move the Chemistry book and observe what happens. Note that the interactive elements in this sim have simple description that can be accessed using a screen reader.

Sample Learning Goals

  • Describe a model for friction a molecular level.
  • Describe matter in terms of molecular motion. The description should include: diagrams to support the description, how the temperature affects the image, what are the differences and similarities between solid, liquid and gas particle motion; how the size and speed of gas molecules relate to everyday objects.
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License:[Source phet ]April 30, 2019, 8:49 p.m.

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